The MYCOMYCETES are not entirely aquatic in habit; they have hyphæ with _transverse walls_, but _no sexual reproductive organs_. The asexual reproduction takes place in very different ways; by endospores (in asci), conidia, basidiospores, chlamydospores, and oidia. Swarmspores are never found. Two chief methods of reproduction may be distinguished, and hence the class may be divided into two large sub-classes:--the ASCOMYCETES (with asci), and the BASIDIOMYCETES (with basidia). Sub-Class 1. =Ascomycetes.= The main characteristic which distinguishes the Ascomycetes is the _ascus_; a name given to a sporangium of a definite shape and size, and containing a definite number of spores. The shape is generally club-like or spherical, the number of spores 8 (in some 2, 4, 16 or more), see Figs. 103, 105, 108, 110, 113, 116, 120, 121, 123, 129. In the lowest forms, the EXOASCI, the ascus springs directly from the mycelium without the formation of a fruit-body (_i.e._ ascocarp). In the higher forms, which contain many species, the CARPOASCI, the asci are united and form ascocarps which may be more or less enclosed (angiocarpic, hemiangiocarpic, and probably gymnocarpic). [Illustration: FIG. 103.--Endogenous formation of spores in _Peziza confluens_. In the youngest asci there is only one nucleus (_b_, _e_); this divides into two (_f_); and the division is repeated so that there are 4 nuclei in _c_ and 8 in _g_. These surround themselves with protoplasm and a cell-wall (_h_, _i_). The protoplasm of the mother-cell is not entirely used up.] The hyphæ of the _Mycelium_ in some remain free, in others they are felted together and form thick strands or flat, cushion-like bodies (compare in particular the stromata of the Pyrenomycetes). Some species form _sclerotia_ (Figs. 116, 128). Asexual reproduction by means of _conidia_ is known in many species as the principal means of reproduction, and the one which affords the most rapid means of distribution. The conidia may be produced on conidiophores (Fig. 109), in conidial-layers (Fig. 122), and often in conidiocarps (pycnidia, Figs. 120 _d_, _e_; 123 _a_; 124 _b._). These last occur partly as the so-called “spermogonia” (that is, pycnidia with microconidia). The conidiophores never approach the basidia.